Friday, April 01, 2016
The KDKA Story - The Early Shortwave Era
According to historical information from mediumwave station KDKA in Pittsburgh, Pennsylvania, Dr. Frank Conrad made his earliest observations regarding the propagation of radio signals in the shortwave spectrum during the year 1920. What he observed was that harmonics from longwave and mediumwave transmitters often propagated with a better signal and wider coverage on shortwave than was available from the fundamental longwave or mediumwave signal itself. This phenomenon led him to begin a serious study of the possible advantages to be obtained with deliberate transmissions in what has since become the shortwave bands.
A few months later in the early Spring of the following year 1921, Conrad began experimental transmissions from his own home grown amateur station 8XK on the second floor in the family garage at the corner of Penn and Peebles streets in Wilkinsburg. His experimental transmissions on 100 meters provided good reception at amateur stations of friends in Boston.
Then in 1922, Conrad directed the construction of a 1 kW shortwave transmitter at the Westinghouse factory complex in East Pittsburgh. In August, this new transmitter was installed in the wooden shack on top of the eight storey Building K where it was taken into experimental service under the callsign 8XS.
Black and white photographs taken during this era show that this wooden shack was located on top at the western end of Building K, and building K itself was the southern most tall building in a small cluster of equal height high rise factory buildings in East Pittsburgh. At the time, the mediumwave transmitter for KDKA was also still located inside this roof top shack, and the shortwave antenna for 8XS was affixed to the same flat roof top.
The shortwave antenna for the transmissions on 100 meters (3 MHz) was 40 ft long with a height of 35 feet above the roof top. The flat top antenna consisted of apparently 5 parallel wires that were end fed at the western end from a two wire open feed line. The program feed for experimental transmissions from 8XS were taken from the regular scheduling of KDKA on mediumwave.
Beginning on March 4 of the next year (1923), station 8XS began a daily program feed on shortwave to a new mediumwave station, KDPM, located at another Westinghouse facility in Cleveland Ohio. This program relay from KDKA was on the air for several hours every evening.
Then, eight months later on November 22, the KDKA mediumwave programing was relayed on shortwave to another mediumwave station, this time KFKX at Hastings Nebraska, near the geographic center of the continental United States. Station KFKX fed this program stream into two transmitters; mediumwave for local coverage and shortwave for pickup and local mediumwave coverage in California.
The shortwave relays from 8XS in East Pittsburgh to the two distant mediumwave stations, KDPM Cleveland and KFKX Hastings. was discontinued soon afterwards due to the poor quality of the retransmitted programing.
In July 1924, both the mediumwave and shortwave facilities of KDKA were transferred from the factory roof top in East Pittsburgh to another Westinghouse facility, this time on Greensburg Pike in Forest Hills. At this new location, just one mile distant from the original East Pittsburgh location, a separate single story brick and concrete transmitter building was constructed.
Transmitters for both mediumwave and shortwave were installed, and a 50 feet long copper tube was attached to a wooden pole as the antenna for the shortwave transmissions. At this new location, the shortwave callsign 8XS was relinquished, and the license for Conrad’s internationally known personal 8XK callsign was transferred to Westinghouse.
In April 1928, one international radio columnist described the shortwave signal from KDKA-8XK on 26 meters as very sharp and difficult to tune, and on 62 meters as strong with garbled modulation. During this same year, international radio regulations promulgated in the United States required the insertion of the letter W as the first letter in the callsign, and thus 8XK became W8XK.
In an endeavor to improve mediumwave signal coverage into the main population areas of Pittsburgh, another move was staged in 1931. A huge new station was constructed on a site in Saxonburg, after a total of 62 different sites in the greater Pittsburgh areas had been examined and tested.
In honor of KDKA and as a welcome to their community, the local civic officials changed the name of the highway on which the station would be built to KDKA Boulevard. Previously various stretches of this highway were gazetted under different names. However, give a year or two later, and KDKA Boulevard was re-gazetted as Saxonburg Boulevard.
A new transmitter building was constructed at Saxonburg on a property of 130 acres and four new shortwave transmitters at a power level of 40 kW each were constructed on site. The mediumwave KDKA transmitters were installed in the north end of the building, and the shortwave transmitters were installed in the south end.
It was stated at this stage, that the huge new 400 kW super power mediumwave transmitter was rated at the very strange reckoning of 500 horsepower; that the very first KDKA transmitter 11 years earlier weighed just 500 pounds; and also that the combined weight of all of the mediumwave and shortwave transmitters at the new Saxonburg site in 1931 weighed a staggering 164 tons.